Tài liệu MEASUREMENTS OF OUTDOOR AIR POLLUTION FROM SECONDHAND SMOKE ON THE UMBC CAMPUS pdf

MEASUREMENTS OF OUTDOOR AIR POLLUTION

FROM SECONDHAND SMOKE ON THE UMBC CAMPUS

James Repace, MSc.

Repace Associates, Inc.

101 Felicia Lane

Bowie, MD 20720

www.repace.com

June 1, 2005

Introduction.

Individual cigarettes are point sources of air pollution; smoking in groups

becomes an area source. Outdoor air pollutants from individual point sources are subject

to plume rise if the temperature of the smoke plume is hotter than the surrounding air;

however if the plume has a small cross-section, as for a cigarette, it will rapidly cool and

lose its upward momentum, and then will subside as the combustion particles and gases

are heavier than air. Thus, in the case of no wind, the cigarette plume will rise to a

certain height and then descend, and for a group of smokers, for example sitting in an

outdoor cafe, on a hospital patio, or in stadium seats, their smoke will tend to saturate the

local area with secondhand smoke (SHS). In the case where there is wind, the amount of

thermally-induced plume rise is inversely proportional to the wind velocity --

doubling the wind velocity will halve the plume rise. In this case, the cigarette plume

will resemble a cone tilted at an angle to the vertical. The width of the cone and its angle

with the ground will depend upon the wind velocity: a higher wind will create a

more horizontal but wider cone (due to increased turbulence), with uncertain impact on

exposure to SHS for downwind nonsmokers. If there are multiple cigarette sources,

the downwind concentrations will consist of multiple intersecting cones, i.e., overlapping

plumes. As the wind direction changes, SHS pollution will be spread in various

directions, fumigating downwind nonsmokers.

SHS contains a large quantity of respirable particles, which can cause breathing

difficulty for those with chronic respiratory diseases or trigger an asthmatic attack in

those with disabling asthma. For the remainder of nonsmokers, Junker et al. report eye,

nasal and throat irritation thresholds for 24 healthy young adult females for repeated

exposures over the course of 2 hours, corresponding to an SHS-PM2.5 concentration of

about 4.4 micrograms per cubic meter (µg/m3

) (Junker, 2001).

Very few published data are available on outdoor levels of SHS. A California Air

Resources Board study (CARB, 2003), measured 1 and 8 hour time-weighted average

nicotine concentrations outside an airport, college, government center, office complex,

and amusement park, found that at these typical outdoor locations, Californians may be

exposed to SHS levels previously associated only with indoor SHS concentrations.

Concentrations were strongly affected by counts of the number of smokers and

moderately affected by the size of the smoking area and the measured wind speed. The

CARB study indicated that outdoor SHS concentrations are detectable and sometimes

comparable to indoor concentrations, and demonstrates that the number of cigarettes

being smoked (i.e., total source strength), the position of smokers relative to the receptor,